I think other names are Dukascopy, MB Trading, IBFX, the Hotspot FX from Mirus Futures, FXCM apparently has a new ECN. I can't think of them all but only have experience right now with GFT Forex. They don't claim to be an ECN but I traded single mini lots with no apparent problem (and that's with profits I mean, lol).
We asked the same question. The problem is that they all draw from different liquidity providers who in themselves have different markets. So even if you could see their "internal" prices, who knows what they show us traders?!?! The BIG BIG question is whether they create a market "just for you". Here's how we answered the question. We are autotraders. So we put the exact same autotrading systems on a LIVE account, and another mirrored on a DEMO account. Then took a look at the results. The bottom line, your LIVE quotes WILL be different from your DEMO quotes. If you are flat, you probably won't see a difference. BUT, if you are in a LIVE trade, that's when you see the difference. If you are in a WINNING trade, strangely our spread got wider. How strange. LOSING trades, suddenly our stop loss got hit a lot, lot more than in the DEMO trades. How strange. Who did these "strange" things to us? It's not my place to bash brokers (many of which were in your lists), but let's suffice it to say... we eventually had to come up with our own solution : - ) Trader 5of7 @ TheCollectiveFX.com
There is nothing in your post... That shows your claims are statistically significant... And using "DEMO" accounts for ANYTHING is highly suspect. Market makers are in direct competition with active traders... And will use CLASSIC legal and illegal techniques... To take your money... So your "analysis" is a big yawn. Frankly... If you cannot take money away from Market Makers in the long run... Your operation is at a disadvantage... And your results will be suboptimal.
You are quite right, without hard numbers and showing significance in a differential, there isn't a lot to be said. The post was intended to show one methodology in directly testing a broker, instead of just asking if they create or skew their market. I also don't want to bash brokers here, since the ones we tested and left were quite popular here. We long since left them and ended up doing our own thing because of the statistical significance (for us). But it is an easy and valid test for any autotrader to "test for themselves" if their broker is indeed shifting them and skewing their trade and equity curve results. It was done to us, and since no strategy performs the same in the future as it did in the past, we often blame the strategy for "going bad". So the only true test is an A B test live/demo, and it's easy.
IB is one of the most sophisticated MM in the world... And Market Making on IDEALPRO is not exactly rocket science... With the 3-4 pip spreads I see in USD.CAD most of the time... It's very lucrative indeed... So I'm sure IB is by far the biggest player on their own ECN.
No, the only true test would be live/live with identical opposite positions, a live/demo comparison would be meaningless. Demo accounts aren't intended for comparing quotes (although I'm told some do use the same feed but with fewer quote updates) or testing the efficiency or integrity of your broker, they're for familiarizing yourself with the trading platform and it's features and getting used to placing orders and executing/managing trades without risking real money. Brokers also use their demo server and platform for testing updates and improvements in the simulated environment of a demo before releasing them on the live version.